Prior to the present invention, various methods were evaluated for treating rock to render the rock more resistant to environmental degradation. There have been many studies and methods of improving the quality of building stone and monuments, and limited study has been devoted to coarse aggregate quality improvement.
One study directed to aggregate improvement is shown by the interim report of May 1977, revised and updated January 1978, report PTI 7707 of the Pennsylvania Transportation Institute of Pennsylvania State University of P. V. Cady, "Upgrading of Poor or Marginal Aggregates for PCC and Bituminous Pavements." Various organic materials were evaluated as treating agents for improving the resistance of aggregate to degradation. Although valuable information has been generated from the aforementioned study, a satisfactory solution to the problem of aggregate degradation resulting from exposure to adverse environmental conditions including air pollution, moisture, or inorganic salt contact has not been found. Improvement has been noted by using organic materials, such as epoxy resins, methyl methacrylate, etc., to treat marginal aggregate, but the degree of aggregate upgrading achieved has not warranted the cost of using such material unless the organics were extensively diluted in polluting organic solvents.
Standard engineering tests can be performed to predict the quality of aggregate. One procedure, for example, has been the magnesium or sodium sulfate soundness test, ASTM C88-76. In many instances, local high quality course aggregate is not available for building construction and must be obtained at a high transportation cost. Various procedures have been used in an attempt to improve the quality of marginal or submarginal rock, for example, argillaceous limestone, highly crystalline limestone and graywacke sandstone to upgrade such material for use in portland cement or bituminous concrete. Procedures of the prior art have been found to be unacceptable because of economic or environmental reasons, or the treated rock failed to survive the magnesium or sodium sulfate soundness test.
Improved results have been achieved as shown by U.S. Pat. No. 4,256,501 of George M. Banino, based on the use of an organic solvent mixture of an organic condensation polymer and an aliphatic polyamine. However, organic solvent can present environmental pollution problem. In addition, the aforementioned aryl condensation polymer, for example, silicon-polycarbonate block polymers, for example, silicone-polycarbonate block polymers can significantly increase the cost of such treatment due to the expense of the starting reactants.
Additional improvements have been achieved with upgrading rock and aggregate by treating the rock with an aqueous polyelectrolyte solution having at least 1% by weight of polyelectrolyte, as shown by LeGrand, U.S. Pat. No. 4,341,824, assigned to the same assignee as the present invention and incorporated herein by reference. Although improved resistance to weatherability can be imparted to the resulting treated rock or aggregate, experience has shown that significant discoloration of the treated rock surface can often occur which may be the result of biological action. We have evaluated a variety of materials as possible "pore blockers" to improve the effectiveness of the aforedescribed rock treatment method.
The present invention is based on our discovery that polyglycols having a molecular weight in the range of from about 200 to 4000 will substantially enhance the weatherability of rock treated in accordance with our method shown in U.S. Pat. No. 4,341,824.